Danger to patients seen in repeated tests

A Yale physician warns colleagues that overuse of CT scans can increase health risks from radiation.

Since the 1970s, computed tomography (CT) has become an increasingly important diagnostic tool whose use has expanded in recent years to replace such conventional procedures as X-rays and ultrasound. But greater dependence on this imaging technique comes at a price: increased exposure to radiation that could increase a patient’s risk of cancer.

In the keynote address at the 43rd National Council on Radiation Protection and Measurements meeting in April, James A. Brink, M.D., professor and chair of diagnostic radiology, emphasized that physicians need to be more aware of the risk of CT and other imaging devices that use radiation. The number of CT exams administered each year in the United States has increased exponentially, growing from 3 million in 1981 to 63 million in 2005. CT scans commonly give the patient a dose of 10 to 25 millisieverts (mSv), compared to 0.10 mSv for a chest X-ray. But even those low-dose exposures typical of CT scans can increase the risk of cancer, according to the Radiation Effects Research Foundation, formerly the Atomic Bomb Casualty Commission, which studies the long-term effects of radiation from the uranium fission bombs detonated at Hiroshima and Nagasaki. That means that patients who undergo numerous CT scans, which is not uncommon, may be in the medium-dose exposure range of the atomic bomb. And smaller doses have a cumulative effect. “That’s important, because if you do several low-dose CT scans, they add up to a larger dose that has the same risk,” said Brink.

In the United States, medical necessity and the judgment of physicians determine whether CT scans will be approved, but radiation exposure is not part of the equation, according to Brink. In Europe, however, each country regulates exposure from CT and other imaging modalities that use radiation. “I think we’re at least a decade behind Europe in terms of attention and regulation regarding medical radiation,” Brink said.

Although Brink is quick to point out that CT has an important place in diagnosis, he also notes that there are a number of ways to control the radiation exposure it entails. “CT should be avoided when MRI or ultrasound is of comparable diagnostic utility,” he said, citing one patient who had 18 CT scans over six years for flank pain, a symptom that usually indicates kidney problems. “He probably only needed the first one and didn’t need the next 17.” In addition, physicians should avoid repetitive exams, tailoring them to the individual patient and the individual application. Manufacturers provide tools to alter the technical parameters of scans, so that a patient having a CT for kidney stones, for example, won’t receive as much radiation as a patient undergoing a scan for metastatic colon cancer.

Since physicians can’t take steps to avoid or reduce exposure if they aren’t aware that the problem exists, education is perhaps the most important component of controlling exposure. In a 2004 study at Yale, Brink and colleagues found that only 9 percent of emergency physicians who had ordered CT scans for pelvic pain over a two-week period believed there is an increased cancer risk from CT. When asked how many chest X-rays are equivalent to one CT, 44 percent of radiologists thought it was equal to between one and 10 chest X-rays—the correct answer is between 100 and 250. “Even radiologists didn’t appreciate the difference,” said Brink. “It shows that education is lacking across the board.”

—Jill Max

Yale joins national effort to reconsider the benefits of hormone therapy

In 2002, the Women’s Health Initiative (WHI), a research program begun in 1991 by the National Heart, Lung, and Blood Institute to address common health issues in postmenopausal women, issued an explosive report. Women who had had hormone replacement therapy (HRT)—a popular and highly recommended method of reducing the discomforts of menopause—were at greater risk of having heart attacks. This news—which was at odds with previous research—rocked the medical and lay communities and prompted many women and their doctors to abandon HRT.

But some researchers had doubts about the study; could limitations in the data analysis have skewed the results? Noting that the WHI studied older women, these researchers questioned whether HRT might provide a higher degree of protection for younger women who had recently entered menopause.

The Kronos Early Estrogen Prevention Study (KEEPS), coordinated by the Kronos Longevity Research Institute in Phoenix, is an effort to answer this question. Nine sites around the country, including the School of Medicine, are participating in a five-year study of 720 women to determine whether beginning hormone therapy in recently menopausal women (ages 42 to 58) protects against atherosclerosis, the major cause of heart attacks.

The principal investigator of the Yale portion of the study is Hugh S. Taylor, M.D., professor of obstetrics, gynecology and reproductive sciences and of molecular, cellular and developmental biology, and director of the department’s division of reproductive endocrinology and infertility. Ninety menopausal women who are within three years of their last period will receive one of three regimens—progestin plus an estrogen patch; oral estrogen; or progestin plus a placebo. Researchers will monitor the effects of estrogen on the subjects’ cardiovascular systems over four years, studying such markers as coronary calcium levels and the thickness of the walls of the carotid artery.

“We want to look at women from the beginning, before atherosclerosis has already started to develop,” Taylor said. The problem with the WHI study, he said, is that researchers looked at women who were already more than a decade past their last period. “It was too late. Those women had already started showing signs of heart disease.”

KEEPS will also look at cholesterol levels and other markers to explore which hormone delivery system is better: transdermal or oral. Transdermal estrogen is thought to be safer because it isn’t processed by the liver in high concentrations.

In addition to these two studies, each KEEPS site is conducting its own ancillary studies. Yale researchers plan to look at estrogen’s effects on skin integrity, bone density, moods, cognition (including memory) and heart rhythms.

Last spring the WHI followed up on its initial research with a study of younger women. Its findings suggest that the KEEPS study may yield encouraging news for women. WHI found a 24 percent reduction in risk of coronary heart disease in women starting HRT less than 10 years after menopause and a 30 percent reduction in overall deaths among women ages 50 to 59 using HRT. And in June, a report by WHI researchers published in The New England Journal of Medicine found that women who take estrogen for seven years after menopause had a lower risk of calcification of the arteries.

—Jennifer Kaylin

A podcast of Hugh Taylor speaking on this subject can be found on the Yale page on iTunes U. Visit itunes.yale.edu or launch iTunes, then select Yale from the offerings under iTunes U. The podcast is included under “Yale Health & Medicine.”

et cetera

Errors and transplant patients

Patients recovering from organ transplants run a high risk of medication errors that can land them back in the hospital, according to a Yale study published in the Archives of Surgery in March.

In the years after surgery, liver, kidney or pancreas transplant recipients took an average of 10.9 medications. The study found 149 errors occurring in 93 patients, with 32 percent resulting in invasive procedures, rejection or failed transplants.

In more than half the cases—56 percent—patients didn’t follow instructions. In other cases, pharmacists substituted generic for brand-name medications or declined to provide the proper medications out of concerns about adverse drug interactions.

“Once the prescription is ordered, we have no routine feedback from the patient, pharmacy or insurer to know whether the medication is being used,” said lead author Amy L. Friedman, M.D., associate professor of surgery. Every encounter with a patient should be viewed as an opportunity to clarify which medications are being taken.

—John Dillon

New treatment for SVCS

About 15,000 people in the United States have superior vena cava syndrome (SVCS), a blockage of the large vein that carries blood from the head and upper body to the heart. Signs of the syndrome, which is usually caused by a malignancy pressing on the vein, include facial swelling, headache and visual disturbances.

“The superior vena cava syndrome is often clinically striking but rarely requires emergency intervention,” said Lynn D. Wilson, M.D., M.P.H. ’86, professor and vice chair of therapeutic radiology and professor of dermatology, lead author of a paper published in The New England Journal of Medicine in May. In the paper, Wilson and colleagues argue for dealing with the underlying cause—the tumor.

Wilson said, “Deterring from a multidisciplinary management plan and focusing only on the effects of the syndrome should be discouraged.”

—J.C.


			Originally published in Yale Medicine, Autumn 2007. Copyright © 2007 Yale University School of Medicine. All rights reserved.